Retaining system for lens holder - includes groove shaped to allow resilient centering ring to expand radially under compression

摘要

The lens holder, which may be shaped to hold e.g. three lenses, has a groove (7) to hold an o-ring (6) to retain the lens (3) in position. The ring is of resilient material, and the groove is shaped in cross section to give a good centering position. In one form this section can be rectangular, positioned so that the ring is forced radially outwards when compressed against the edge of the lens, which is supported by a shoulder (5) at the rear. In alternative forms, the groove section may be semicircular or trapezoidal.